Resiliently mounted contact slidable on inductive coil



Sept- 6, 1966 N. BERMAN ETAL RESILIENTLY MOUNTED CONTACT SLIDABLE ONINDUCTIVE COIL 4 Sheets-Sheet 1 Original Filed April 18, 1962 INVENTORSLEO/V BER/74h BY 60 SE/DEN vj Mao I MM W ATTORNEYS.

Sept- 6, 1966 N. BERMAN ETAL RESILIENTLY MOUNTED CONTACT SLIDABLE ONINDUCTIVE COIL Original Filed April 18, 1962 4 Sheets-Sheet 2 INVE NTORS n zzso/v BER/MW HUGO JE/DEW P 6, 1966 N. BERMAN ETAL. 3,271,715

RESILIENTLY MOUNTED CONTACT SLIDABLE 0N INDUCTIVE COIL Original FiledApril 18, 1962 4 Sheets-Sheet 3 INVENTORS NELSON HERMAN HUGO SEIDEN p 6,1966 N. BERMAN ETAL 3,271,715

RESILIENTLY MOUNTED CONTACT SLIDABLE ON INDUCTIVE COIL Original FiledApril 18, 1962 4 Sheets-Sheet 4 FIG.

I77 925 I93 20 I80 r I 192 I 2, I83 I I 18 M 7 l I821) I C n l\ 7 50I8Io.

INVENTORS NELSON BERMAN HUGO SEIDEN United States Patent 3,271,715RESILIENTLY MOUNTED CONTACT SLIDABLE 0N INDUCTHVE C(lllL Nelson Berman,New Hyde Park, and Hugo Seiden, Brooklyn, N.Y., and Joseph R. Roy,Wapping, Conn, assignors to JFD Electronics Corporation, Brooklyn, N.Y.,an organization of New York Original application Apr. 18, 1962, Ser. No.188,458. Divided and this application May 7, 1965, Ser.

2 Claims. (Cl. 336137) This application is a division of the applicantscopending parent application, serial No. 188,458 filed April 18, 1962,which has been abandoned.

This invention relates to improvements in ganged tuning devices, and inparticular relates to an improved ganged tuning device wherein theindividual tuning elements are of the slug or plunger type.

One object of this invention is to provide a ganged slug or plungertuning device which is mechanically easy and economical to manufactureand assemble, with a minimum of mechanical and electrical alignmentproblerns.

Another object of this invention is to provide a tuning device of theabove-described type which provides simple automatic means forcompensating for misalignment of respective tuning plungers or slugs inthe tubular shells in which they slide.

Another object of the invention is to provide improved bea-ring meansfor the main drive shaft of a ganged tuning device or other device, sothat the drive shaft is free from backlash.

Another object of the invention is to provide improved means forstopping the turning of the main drive shaft of a ganged tuning deviceor other device, at the extreme limits of the desired range of turningof such main drive shaft, so as to prevent damage to the drive mechanismand limit the tuning range.

Another object of the invention is to provide a ganged slug or plungertuning device, the resonance frequency tolerance or each individualtuning device being extremely low.

Another object of the invention is to provide a tuning device of theabove type wherein the frequency as a function of angle rotation of themain drive shaft can readily be controlled: for example, by having thefrequency change linearly with respect to angle of rotation.

Another object of the invention is to provide a multiganged tuner whichmay be readily designed so as to have desired electricalcharacteristics: for example, resonant frequency as a linear function ofcontrol shaft rotation, and constant ratio of inductance to capacity ofeach capacity-inductance section at all resonance frequencies.

Another object of the invention is to provide an improved -tuner withreduced microphonics under conditions of vibration encountered duringoperation.

Another "object of the invention is to provide a tuner of theabove-described type having simple independent means for adjusting ortrimming each capacitive or inductive element.

Another object of the invention is to provide an improved inductancetuning element for use in a tuner of the above-described type.

Another object of this invention is to provide a multi- 3,271,715Patented Sept. 6, 1966 lCC ganged tuner which is consider-ably smallerthan plate meshing air dielectric capacitors commonly used.

In accordance with preferred embodiments of the invention, the tuningdevice comprises an enclosed cylindrical housing of selected crosssectional configuration having a longitudinal axis and front and rearend walls, as Well as a transverse partition fixedly mounted in thehousing intermediate said end walls.

The device further comprises a plurality of longitudinally extendingreaotance tubes fixed to the partition on the rear thereof. Some or allof these tubes may be capacitor tubes made of dielectric material andhaving a conductive coating between concentric layers of the dielectricmaterial. Some or all of these tubes may be inductance tubes made ofinsulating material and having a helically wound Wire embedded in thewall of the bore thereof.

In accordance with the invention, there is further provided an axiallyextending drive shaft which extends through appropriate bearings of thepartition and the front Wall. The drive shaft also extends forwardly ofthe front wall and is there provided with a knob for turning purposes.There is further provided a transverse plate axially slidably andnon-rotatably mounted in the housing between the partition and the frontwall and coupled to the drive shaft for axial movement of the transverseplate in response to turning of the drive shaft.

Stiff wires are mounted on the plate so as to extend longitudinallyrearwa-rdly thereof, with the position of each wire being individuallyadjust-able for trimming purposes. 'The wires extend respectively intothe respective tubes and are transversely suitably flexible andresilient. A slug member is mounted on the end of each wire within itsassociated tube. In the case of the capacitative reactor, the slugmember may be in the form of a conductive hollow piston. In the case ofan inductance element, the slug member may be in the form of a flat discwhich makes wiping contact with the spirally mounted wire inside thetube. The conductive coatings and the spirally wound wires arerespectively shaped in any desired manner so as to produce varyingelectric capacity and inductance characteristics of the reaotanceelements as the result of axial movement of the slug elements. Further,the various reactance elements may be electrically combined in externalcircuits so as to provide any desired reaotance combinations.

As an important feature of the invention, the wires can flex somewhat soas to accommodate misalignments of the wires, or of the mechanism.generally, relative to the tubes during axial movement of the plate.This permits the desired tight fit of the slug elements within the tubeto decrease the air gap, to reduce piston flutter during vibration andto reduce microphonics, while, at the same time, minimizing the need foraccurate machining of the assembly which carries the slug elements.

It is extremely important, in a tuning device of this type, to preventbacklash of the control shaft. Such prevention of backlash can also beimportant in other devices. In accordance with one preferred embodimentof the invention, the control shaft has a helical squareshaped grooveand an outer periphery. A driven collar member is coupled to theaforesaid plate which carries the wires which support the slug elements.A further collar member is also mounted upon the control shaft and islongitudinally displaced from the driven collar memher. These collarmembers are longer than the width of the helical groove. The collarmembers are non-rotatably coupled by a spring or the like which urgesthe collar members in opposite direction. Bearing means are respectivelymounted on the respective collar members and extend slidably into thespiral groove and engage rollingly against the respective side walls ofthe groove. The action of the spring maintains the respective bearingmeans frictionally against the respective walls of the groove so as toprevent backlash of the shaft relative to the driven collar member.

Other objects and advantages of the invention will become apparent fromthe following description, in con- 'junction with the annexed drawings,in which preferred embodiments of the invention are disclosed.

In the drawings, FIG. 1 is'a perspective view of a tuner in accordancewith this invention.

FIG. 2 is a view similar to FIG. 1, but with the peripheral wall of thehousing removed and drawn to a somewhat enlarged scale.

FIG. 3 is a longitudinal sectional line 33 of FIG. 1.

FIG. 4 is a section on line 44 of FIG. 3.

FIG. 5 is a section on line 55 of FIG. 3.

FIG. 6 is a detail section on lines 6-6 of FIG. 3.

FIG. 7 is a fragmentary detail view similar to FIG. 3, showing a portionof one of the capacitor elements in an enlarged scale.

.10 having a peripheral wall 11 which is shown as generally triangularin cross section with rounded corners 11a. However, as will be explainedin somewhat more detail below, any convenient cross sectional shape ofthe housing peripheral wall 11 may be provided. Said housing 10 may bemade of metal or any other suitable material. Housing 10 has a rearclosure wall 15, shown in FIG. 3, which is optionally integral with sideperipheral wall 11. Housing 10 has a front closure wall 14 whichoverlies the front edge of peripheral wall '11 and which has a rear boss14a which extends frictionally into peripheral wall 11. Said front wall14 is secured to peripheral wall 11 by any suitable sealing means (notshown), enabling housing 10 to be sealed against dust and other externalconditions. i

The tuning device further comprises a transverse partition wall 17 whichis fixed in place within the peripheral 'wall intermediate the end walls14 and 15.

Partition 17 has a central opening 17a, the rear portion 17b of which isof increased diameter. Hollow, cylindrical, axially extending body 18.is positioned in the compartment 20 between partition 17 and rear wall15, said 'body 18 extending frictionally into opening portion 17b andagainst the shoulder between hole portions 17a and 17b. Body 18 has athick rear transverse wall 18a.

In addition to the body 18, a plurality of reactance tubes 30 and 31 arealso disposed within compartment 20. Illustratively, nine tubes areshown; but this number may be varied. Optionally, only tubes 30 or onlytubes 31 may be used. Illustratively, the drawings show eight tubes 30and one tube 31.

Each said tube 30 or 31 is made of an appropriate dielectric material,such as glass, although it will be apparent that the tube 31, which ispart of an inductance, can be made of any suitable insulating material.The front end of each said tube 30 and 31 extends frictionally into anappropriate aperture 22 of partition 17, as shown in FIG. 3. Tube 30 or31 as the case may be,

is soldered within the aperture 22 in which it is received, by means ofa ring of solder 21 which extends into an appropriate annular groove ofpartition 17 opening upon aperture 22. In other words, the solderingsecuring the tube to the partition is received internally within thepartition. Each said tube 30 or 31 extends longitudinally rearwardlyfrom partition 17 to a point spaced slightly forwardly of rear wall 15.

Each inductance tube 31 has a metal coil 32 in the bore thereof. Thesuccessive turns of coil 32 are embedded to approximately half thediameter of the wire in a complementary groove 32a formed in the tubewall. The pitch of the turns of coil 32 has a selected variationcorresponding to the desired inductance curve of the device.Illustratively, the longitudinal spacing between successive turns ofcoil 32 is shown as increasing from front to rear.

At the rear of tube 31, a conductive coating 23- is deposited on theinside of the bore of the tube, in contact with the rear end of the wire32. Said coating 23 extends around the rear end of the tube and thenforms a coating 23a around the outside thereof.

Each tube 30 includes an inner glass tubular portion 35 upon which isprovided an outer conductive coating 36. The tube 35 and its coating 36are further intimately coated by an outer tubular layer 25, also ofglass. Said coating 36 has a selected configuration corresponding to thedesired capacitance curve of the device. Thus, as illustrativelyshown'in FIG. 3, the coating 36 may be cut away at the front so as tovary the circumferential extent of the coating, such variation occurringfrom minimum circumferential extent adjacent partition 17 to a rearwardpoint at which the coating extends completely around the periphery ofthe tube. Behind this point, the coating 36 communicates with a coatingband 38 which is cylindrical and which is between the layers 35 and 25and which extends to the rear end of tube 30. At the rear end of thetube, the coating 38 is extended outwardly over the rear end of theouter tube portion 25 and then is further extended around the outerperiphery of tube portion 25 to form a cylindrical outer band 38b. Therear end of of each of the tubes 30 and 31 is closed by a transversemetal end cap 26 which makes electrical contact with the conductive band38b or 23a, as the case may be. Cap 26 is secured to the outside of band38b or 23a by means of solder 2. Inwardly of coating 38 or 23, the frontface of cap 26 is covered by insulating disc 3 which prevents electricalcontact between piston or disc 97 and cap 26. Said end cap 26 has a rearterminal boss 40 which is connected by wire 41 to a metal connector 42which extends through an aperture 43 in the rear wall 15, said connector'42 being sealed in said aperture 43 by a gasket 44. Rearwardly of wall15, the wires 42 may be connected in any desired circuit arrangement.

In accordance with the invention, there is provided an axially extendingdrive shaft 50 and bearing means for said drive shaft 50. Specifically,an aperture 13c is formed centrally in wall 18a, the front portion ofaperture 18c, designated by the reference numeral 1812, being ofincreased diameter. A ball bearing assembly 51 is fixed within theaperture portion 18b having an outer race 51a, an inner race 51b,mounted upon reduced rear end portion 50a of shaft 50, and the usualballs 52 between the races.

Further bearing means and sealing means areprovided in Wall 14. Saidwall 14 has a central, cylindrical axial front boss 16. A through bore16a extends through boss 16 and wall 14, the rear end 16b of bore 16abeing of in- Shaft portion 50d extends forwardly of shaft portion 500.Knurled knob 60 is fixedly mounted upon shaft portion 50d by means of aset screw 61. Cylindrical flange 60a extends rearwardly from knob 60,almost to wall 14, and is radially spaced from shaft portion 500. Aplurality of circular discs (FIGS. 3 and 5) are turnably mounted uponboss 16 and are turnable within flange 60a. Each disc 63 has apart-circular slot 64, illustratively 270 in length as shown in FIG. 5.Longitudinally extending pins 65 are fixed to the front face of eachdisc 63, in circumferential alignment with slot 64, and symmetricallyplaced circumferentially with respect to slot 64. There are two suchpins 65, illustratively spaced 60 apart as shown in FIG. 5.

The pins 65 of each disc 63 extend slidably into the slot 64 of disc 63just in front thereof, as shown in FIG. 3. The pins 65 of the frontdiscs 63 similarly extend into a groove 66 on the rear face of knob 60which corresponds to slots 64. Similarly, pins 67 on the front face ofwall 14 extend into the slots 64 of the rear disc 63.

It will be apparent that a limit of turning of one disc relative toanother is reached when an appropriate pin 65 strikes an appropriate endof slot 64. Illustratively, six discs 63 are shown in FIG. 3. By slightvariation of one or more slots 64 or groove 66, or by slight variationof spacing of one or more pairs of pins 65 or of pins 67, the totalangular movement of knob 60 may illustratively be 1,440 or four turns.While this range of movement has been found convenient, the invention isnot limited to this range. In any event, it will be apparent that apositive stop is provided against the turning of shaft 50 at the limitsof its angular rotation. It will further be apparent that the number ofdiscs or dimensions of slots may be varied to obtain any desired rangeof angular movement of shaft 50.

Also, in accordance with the invention, transverse plate 70 is mountedwithin the casing axially slidably but nonrotatably, between partition17 and front wall 14. In order to support plate 70, a plurality oflongitudinally extending rods 71 are extended between wall 14 andpartition 17. Each rod 71 has a front end screw-threaded extension 71aof reduced diameter which is screwed into an appropriate screw-threadedbore of wall 14, and a rear extension 71b of reduced diameter whichextends through an appropriate aperture of wall 17 and a screw-threadedrearwardly thereof to receive nut 72. Said rods 71, accordingly, notonly serve as guides for plate 70 but also serve to secure partition 17rigidly in place.

Said rods 71 extend slidably through respective sleeve bearings 73 inrespective apertures 74 in plate 70 and accordingly permit axialmovement of plate 70.

.In accordance with the invention, improved means are provided forcoupling shaft 50 to plate 70. Specifically, as particularly shown inFIGS. 8, 9 and 10, shaft 50 is provided with a deep and wide spiralgroove 75 which is square in that the sides of the groove aresubstantially perpendicular to the axis of shaft 50. Said groove 75extends from shaft portion 50b to shaft portion 50a. Plate 70 has ascrew-threaded through bore 76, centrally located. A driven collarmember 77 abuts the rear face of plate 70 and has a forwardscrew-threaded coaxial extension 77a of reduced diameter which isscrewed into bore 76. Collar 77 and its extension 77a have a commonthrough bore 77b through which the outer periphery 75a of shaft 50extends turnably.

A further collar member 78 is located rearwardly of collar 77 and inaxial alignment therewith and has a bore 78a through which the outerperiphery 75a of shaft '50 extends turnably. The collar members 77 and78 are axially spaced. Any appropriate spring means may be employed soas to couple the two collar members 77 and 78 non-rotatably while urgingthe two collar members in opposite direction. In this embodiment, andwithout limitation thereto, said spring takes the form of a metalbellows 79 through the bore 79a of which the shaft outer periphery 75aextends clearingly. The respective ends of the bellows 79 extend aroundand are fixed by any suitable means to the peripheries of driven collarmember 77 and further collar member 78. Bellows 79 is expansi'ble in theusual way so as to urge the collar members 77 and 78 away from eachother, but said bellows substantially resists torque and therebyprevents relative rotation of the members 77 and 78.

Said collar members 77 and 78 have parallel radial through bores 80. Apin 81 extends through each bore 80 and is fixed therein by any suitablemeans (not shown). The inner end of each pin 81 is tapered at 81a and isfixed to one end face of the inner race 82a of a ball bearing assembly82. Bearing assembly 82 has the usual circular outer race 82b coupled tothe inner race by the usual balls 83. Each bearing assembly 82 isreceived within groove 75, and the races 8 2a and 82b turn about aradial axis. For aid in assembly, collars 77 and 78 respectivelyoptionally have radial through bores 80b diametrically aligned withbores 80.

The diameter of the outer peripheral surface of race 82b is less thanthe width of groove 75. Accordingly, as clearly shown in FIG. 8, thespring 79 urges the races 82b oppositely into engagement againstopposite faces of the groove. It will be apparent that when shaft 50turns, the respective surfaces of groove 75 frictionally engage theperipheries of the respective races 82b causing them to turn on theirball bearings. This causes the frontmost race 82b to travel in thegroove 75, thereby carrying the driven collar member 77 in directioncorresponding to the direction of turning of shaft 50. Of course, theplate 70 moves forwardly or rearwardly in unison with the movement ofdriven collar member 77. The provision of the second collar member 78and spring 79 insures the frictional engagement of the front race 82bwith the wall of the groove 75 so as to insure that there will be nobacklash, with rotary movement of shaft 50 being instantly communicatedto the driven collar member 77. The provision of the bearing assembliesinsures that they will move smoothly in the groove without slippage. Thearrangement of a rolling member is superior to the usual arrangement inwhich a driven member has a rigid protuberance riding in the groove. Anadditional advantage of the bearing shaft arrangement is its long life.

In the modification of FIG. 11, only the assembly associated withbushing or collar 177 (corresponding to collar 77), since the assemblyassociated with the bushing or collar corresponding to collar 78 is thesame. Collar 177 has a radial through bore 180, the inner end 180a ofwhich is of reduced diameter.

A pair of inner and outer abutting bearing assemblies 182 and 192 arereceived co-axially within bore 180. Bearing assembly 182 extends to theshoulder defined at the junction of bores 180 and 180a. Bearing assembly182 has outer race 18212 fixed within bore .180, inner race 182a andcoupling balls 183. Similarly, bearing assembly 192 has fixed outer race192b, balls 193 and inner race 192a. Races 192a and 182a are fixedlymounted upon radial shaft 181. Shaft 181 has an inner cylindricalextension 181a of increased diameter which extends clearingly throughbore 18% and into groove 75 of shaft 50.

The opera-tion of the structure of FIG. 11 is essentially the same asthe operation of the structure of FIGS. 8-10. In each instance, a radialmember is turnable about its axis both with respect to the collar andthe shaft groove 75 and is maintained by a spring against the wall ofthe groove.

Plate 70 has a plurality of through apertures (FIG. 3) extendinglongitudinally and in respective alignment with tubes 30 and 31. Aninternally screw-threaded tube or collar 91 is frictionally receivedwithin each bore 90 and protrudes rearwardly of plate 70. A screw 92 isscrewed into each collar 91 and has a front slot 920:. Wall 14 hasscrew-threaded bores 92b in alignment with screws 92 which areordinarily closed by capping screws 920. Each capping screw 920 may beremoved from the outside for access to the slot 92a of screw 92 foradjustment purposes. Once the trimming is done, screw 920 may bereplaced and may seal bore 92b, either by means of a gasket (not shown)or by soldering screw 92c in place, as shown by reference numeral 5.

Stiff longitudinally extending wires 93 are embedded in the screws 92which are in longitudinal registration with the tubes 30. Stiff wires 94which extend longitudinally are embedded in the screws 91 which are inalignment with the tubes 31. These wires 93 and 94 are similar except inlength, and are sufficiently rigid to prevent buckling thereof in thetransport of reactance elements in the manner to be described below.However, the wires 93 and 94 may be flexed transversely resiliently tocorrect misalignments as described below.

Each wire 93 is associated with a hollow cylindrical metal piston 95which extends slidably frictionally into the bore of a respective tube30. Optionally and preferably, as shown in FIG. 6, piston 95 has alongitudinal slot or cut 95a extending its full length and is made ofspring material. Piston 95 is compressed when inserted in tube 30 andits resiliency maintains it tightly against the wall of the bore of tube30. Piston 95 has an intermediate transverse metal partition 96 which isfixed thereto by soldering 96a. The soldering 96a terminates at pointscircumferentially spaced on either side of out 9511 to permit thedesired flexing of the wall of tube 95. Wire 93 extends through a holeof partition 96 in piston 95 and is fixed to partition 96 by anysuitable means, such as rivet head 9311 or welding.

It will be apparent that the capacity of the unit depends upon theconfiguration of coating 36 and upon the longitudinal position of piston95. In addition, slot 95a serves as trimming means to vary the slope ofthe tuning curve. Thus, illustratively, in the shape of the coating 36shown in FIG. 3, it is possible to vary the capacity characteristics ofthe device by varying the turned position of the piston. It will beapparent, for example, that the electrical characteristics will varydepending upon what proportion of the total length of coating is opposedby slot 9 5.

The construction of the capacitor wall (tube 30) makes it possible forthe wall to have an overall thickness of approximately 0.005 inch, witha thin but high coefficient dielectric interposed between the piston andthe coating. This makes it possible to miniaturize the tuner size, ascompared to the size of a conventional air dielectric tuner.

Each wire 94 is slightly longer than wire 93. Adjacent the rear end ofwire 94, it extends into a metal wiper disc 97 of round or circularconfiguration. The diameter of disc 97 is substantially equal to thediameter of the bore of tube 31 less half the diameter of the wire ofcoil 32. Upon longitudinal movement of disc 97, it tracks with the wireof coil 32 and continuously wipes against it, with the wire 94correspondingly oscillating flexibly and resiliently.

The operation of the device should be clear from the foregoing. Byturning knob 60, plate 70 is moved axially depending upon the directionof turning of the knob, thereby correspondingly moving the reactanceelements 95 and 97. As a result, the reactance of the individualinductance and capacitance elements is varied. .Mechanically, in theevent that there is any misalignment or in the further event that thereare any changes in alignment during the longitudinal movement of plates70, so as to tend to cause misalignment of the wires 93 relative to thebores of the various tubes 30 and 31, the wires automatically fiex incompensation. As a result, it is not necessary to provide precisionconstruction of the plate 70 and its mounting means. Furthermore,individual trimming adjustments of the various reactance elements canreadily be obtained by loosening the set screws 92c and turning theadjusting screws 92.

Any desired electrical characteristics can be produced. In theembodiment shown in the drawing, it is noted that the change ofinductance of an inductance element resulting from the axial movement ofplate 70 is inverse to the corresponding change in capacity of acapacity element. By proper shaping of coil 3-2 and of the conductivecoating 36, of electrically coupled capacity and inductance elements, itis possible to maintain a constant ratio between inductance andcapacity, as a result of which the resonant frequency is a linearfunction of control shaft rotation and the impedance of the section isconstant at all resonant frequencies. However, it will be understoodthat the invention is not limited to such an arrangement. It is entirelypossible that the invention may be used to vary only capacitance, onlyinductance or any other combination of capacity and inductances besidesthat iliustrated. There may be additional reactance sections in anyother appropriate geometric relationship, so long asthey are controlledby plate 70. In certain applications, inductance may be kept constantand only capacity varied. In all instances, an important feature is theuse of the stiff wires 93 and 94 adjustably mounted upon plate 70, so asto control the movable reactance elements, thereby eliminating the needfor precise alignment of operating parts and permitting close fit of thepiston 95 and tube 30 for reduction of microphonics. The specificarrangement of the wiper disc 97 and inductance coil 32 is also highlyadvantageous as permitting precise control of inductance with goodelectrical contact throughout the range for operation. It will beapparent that the principle of this construction can also be employed inganged variable resistances.

It will be apparent that any desired cross sectional configuration ofthe tuning device may be used, with any desired combinations ofinductance and capacity elements. The inductance and capacity elementswithin compartment 20 may be individually shielded, by any suitablemeans (not shown), or may be shielded in groups which are to beconnected together in circuit, as desired.

While a preferred embodiment of the invention has been disclosed, andvarious possible changes, omissions and additions have been indicated,it will be apparent that various other changes, omissions and additionscan be made in the invention without departing from the scope and spiritthereof.

What is claimed is:

1. In a tuning device of the type described, an inductor comprising alongitudinally extending insulating tube having a generally spiralgroove on the wall of its bore, a conducting first wire embedded in saidgroove and protruding in said bore and being thereby configured to haveinductance, a support outside said tube and longitudinally opposing anend of said tube and having a longitudinal opening, a conducting secondwire extending slida-bly into said opening and also into said tube,means releasably locking said second wire in said opening, a conductingdisc fixed to said second wire in said tube and of sufficient diameterso that it engages frictionally between said first wire and the wall ofsaid bore, said disc having its longitudinal dimension substantiallyless than the pitch of said groove, means mounting said support and saidtube so that they are relatively longitudinally movable, said secondwire being still but somewhat flexible and resilient so as to move toaccommodate tracking movement of said disc along said first Wire duringrelative 1ongitudinal movement of said support and said tube.

2. In a tuning device of the type described, an inductor comprising aninsulating tube having an axis and having a bore and having a generallyspiral groove on the wall of its bore, a conducting first wire embeddedin said groove and protruding into said bore and being therebyconfigured to have inductance, a conducting second wire, said secondwire being disposed coaxially with said tube and axially and slideablymoveable with respect thereto to extend into and out of said tube, meanssupporting said tube and said second wire, a conducting disc fixed t0said second Wire in said tube and of suflicient diame- 9 ter so that itengages frictionally between said first wire and the Wall of said bore,said disc having its longitudinal dimension substantially less than thepitch of said groove, said second Wire being stifi but somewhat flexibleand resilient so as to move to accommodate tracking 5 movement of saiddisc along said first Wire during relative axial movement of said wireand said tube.

References Cited by the Examiner UNITED STATES PATENTS 10 2,466,2014/1949 Boudreaux 200-136 X 2,483,105 9/1949 Rennick 336136 2,649,5778/1953 Armstrong 336-144 X LARAM-IE E. ASKIN, Primary Examiner.

ROBERT K. SCHABFER, Examiner.

W. M. ASBURY, Assistant Examiner.

1. IN A TUNING DEVICE OF THE TYPE DESCRIBED, AN INDUCTOR COMPRISING ALONGITUDINALLY EXTENDING INSULATING TUBE HAVING A GENERALLY SPIRALGROOVE ON THE WALL OF ITS BORE, A CONDUCTING FIRST WIRE EMBEDDED IN SAIDGROOVE AND PROTRUDING IN SAID BORE AND BEING THEREBY CONFIGURED TO HAVEINDUCTANCE, A SUPPORT OUTSIDE SAID TUBE AND LONGITUDINALLY OPPOSING ANEND OF SAID TUBE AND HAVING A LONGITUDINAL OPENING, A CONDUCTING SECONDWIRE EXTENDING SLIDABLY INTO SAID OPENING AND ALSO INTO SAID TUBE, MEANSRELEASABLY LOCKING SAID SECOND WIRE IN SAID OPENING, A CONDUCTING DISCFIXED TO SAID SECOND WIRE IN SAID TUBE AND OF SUFFICIENT DIAMETER SOTHAT IT ENGAGES FRICTIONAL BETWEEN